IT201800006225A1 - METHOD AND MACHINE FOR THE SURFACE DECORATION OF A BASIC ARTICLE OF THE CERAMIC PROCESSING INDUSTRY - Google Patents

Description

of the patent for industrial invention entitled:

"METHOD AND MACHINE FOR THE SURFACE DECORATION OF A BASIC ARTICLE OF THE CERAMIC WORKING INDUSTRY"

TECHNICAL FIELD

The present invention relates to a method and a machine for the surface decoration of a basic article of the ceramic processing industry, in particular an article comprising ceramic material. The present invention also relates to a method and a plant for manufacturing ceramic articles.

BACKGROUND OF THE INVENTION

In the field of the production of ceramic articles (in particular, slabs; more particularly, tiles) machines for the surface decoration of a basic article are known.

In particular, machines are known which comprise a printing device suitable for applying a design (a graphic) on a basic article in order to decorate it and create an effect that allows to simulate a natural object such as a marble or stone slab. wood.

This type of machines comprise a belt conveyor, which advances the basic article through a printing station, in correspondence with which the aforementioned drawing is applied, and one or more fixed guides, which allow to keep the article correctly oriented. base while it is being fed to the print station.

Typically, the base item is not yet cooked and is therefore delicate. In consideration of this and the fact that it is relatively large and heavy, the basic article can be easily damaged and must, in these cases, be subsequently discarded.

Alternatively or in addition to what is described above, often, in order to avoid areas of the article that are not covered by the drawing, a drawing of larger dimensions than the article is provided. It is clear that, in these cases, there is a greater consumption of ink than is really necessary and the excess ink dirties the machines and the areas close to them in a not inconsiderable way.

To overcome the aforementioned problems, machines without guides designed to orient the base article have been described, but equipped with a scanner placed upstream of the printing station to estimate the orientation of the base article. In use, the design is printed after being rotated in consideration of the estimated orientation of the base article.

These machines have several drawbacks, among these we mention the inability to operate in a simple, fast and accurate way. In other words, the acquisition of data on which to estimate the orientation of the article is slow and not precise and the processing of such data is complex and approximate.

The object of the present invention is to provide a method and a machine for the decoration of a basic article, and a method and a system for the production of ceramic articles, which allow to overcome, at least partially, the drawbacks of the known art and are, at the same time, easy and inexpensive to make.

SUMMARY

According to the present invention there are provided a method and a machine for the surface decoration of a basic article according to what is disclosed in the following independent claims and, preferably, in any one of the claims directly or indirectly dependent on the independent claims.

BRIEF DESCRIPTION OF THE FIGURES

The invention is described below with reference to the attached drawings, which illustrate some examples of non-limiting implementation, in which:

- figure 1 is a schematic and plan view of a machine according to the present invention;

Figure 2 schematically illustrates a step of the method according to the present invention;

Figure 3 is a schematic and plan view of the machine of Figure 1 in a different operating phase;

Figure 4 is a side view of details of the machine of Figure 1;

Figure 5 is a schematic and plan view of the machine of Figure 1 in a further operating step; And

Figure 6 is a schematic and plan view of a portion of the machine of Figure 1 in a different operating phase.

DETAILED DESCRIPTION

In accordance with a first aspect of the present invention, in figure 1 with 1 a machine for the surface decoration of a basic article 2 of the ceramic processing industry is indicated as a whole. Article 2 has at least one surface 3 (oriented upwards) and at least three edges 4, 5 and 6, which are joined together so as to define two edges 7 and 8 (corner).

In particular, the corner 7 is arranged between the edges 5 and 5 and the corner 8 is arranged between the edges 5 and 6.

Typically but not necessarily, article 2 has the shape (in plan) substantially of a quadrilateral. More precisely, article 2 basically has the shape of a parallelepiped. In some specific and non-limiting cases, Article 2 has a substantially rectangular shape (in plan).

Advantageously but not necessarily, at least one of the edges 4, 5 and 6 (in particular, the edges 4 and 6), have a length of at least 1 meter, in particular of at least 1.3 meters.

In particular, the basic article 2 includes (is of) ceramic material.

The machine 2 comprises a conveyor device 9 to convey the basic article 2 along a determined path P, in a direction A of advancement, through a detection station 10 and a printing station 11 arranged downstream of the detection station 10; and a detection device 12, which is arranged in correspondence with the detection station 10 and comprises at least two matrix cameras 13 and 14, which are able to acquire one (only) image 15 of the edge 7 and one (only) image 16 of the corner 8, respectively. Advantageously but not necessarily, the conveyor device 9 is able to advance the article 2 along the path P with a substantially continuous motion (not step by step).

The machine 2 also comprises a control system 17, which is adapted to move (in particular, rotate) a predefined pattern 18 (Figure 2) on the basis of the images acquired by the matrix cameras 13 and 14 so as to obtain a manipulated design 19 (which fits the estimated position / orientation of Article 2); and a printing device 20, which is able to apply (apply) the manipulated design 19 on the surface 3 of the basic article 2.

In particular (Figure 1), the control system 17 is able to estimate a position 21 of the corner 7 and a position 22 of the corner 8 of the images 15 and 16.

More specifically, the control system 17 is adapted to estimate the inclination (orientation) of the base article 2 with respect to the direction A of advancement as a function of positions 21 and 22 so as to obtain an estimated inclination (orientation) , and is adapted to rotate a predefined pattern 18 to be brought back onto said surface as a function of the inclination (orientation) estimated to obtain the manipulated pattern 19.

According to some non-limiting embodiments, the control system 17 is able to estimate an angle θ of inclination of the basic article 2 (more precisely, of the edge 6) with respect to the direction A of advancement, in particular as a function of the position 21 and of position 22. More particularly, the control system 17 is able to estimate the angle θ of inclination with respect to a theoretical reference article 2 '(arranged with its own longitudinal extension in the direction A). More precisely, article 2 'has two edges substantially parallel to direction A (and at least one edge - in particular, two edges - substantially perpendicular to direction A). Article 2 defines a nominal reference position.

In particular, the control system 17 is able to rotate a predefined pattern 18 as a function of the inclination (orientation) estimated to obtain the manipulated pattern 19. In some specific and non-limiting cases, the control system 17 is able to rotate the 18 default design of the inclination angle θ.

According to some non-limiting embodiments, the inclination (the orientation or, more precisely, the inclination angle θ) is estimated by interpolating the positions 21 and 22 and (knowing the shape of the article 2) by determining the angle between the interpolating curve (straight line) and direction A). In addition or alternatively, the inclination (the orientation or, more precisely, the inclination angle θ) is estimated (knowing the shape of the article 2) on the basis of the differences between the X and Y coordinates of the positions 21 and 22.

The X and Y coordinates of a point (or a position) are the coordinates on a plane parallel or coincident to that on which the article 2 lies (the printing surface of) while, in use, it is advanced along the path P In particular, the Y axis (i.e. the Y coordinate axis) is substantially parallel to the A direction (and the X axis - i.e. the X coordinate axis - is substantially perpendicular to the A direction). plane of coordinates X and Y is the plane of surface 3.

More precisely, the plane on which the article 2 lies is an upper support plane of the conveyor device 9, more precisely a movement plane 23 (plane of a movement element 23 '- for example belt, belt, chain and roller conveyor) , adapted to support the article 2 below and to move along (at least part of) path P (in particular, the movement plane 23 extends along - at least part of - path P).

In particular, the control system 17 is able to determine the X and Y coordinates on the basis of what is detected by the cameras 13 and 14. More particularly, the control system 17 is able to determine the X and Y coordinates in a system of reference of the detection device 12 (of cameras 13 and 14). Even more particularly, this reference system is a pixel reference system (as a unit of measurement).

According to some non-limiting embodiments, the control system 17 is adapted to convert the (coordinates of the) positions 21 and 22 acquired in the reference system of the detection device 12 (in pixels) into positions according to a reference system of the device of print 20 (in millimeters).

According to some non-limiting embodiments (such as that illustrated in Figure 1), the control system 17 is connected to the detection device 12 and to the printing device 20, in particular to receive data from the detection device 12 and transmit them to the device In some non-limiting cases, the control system 17 is equipped with a unit directly part of the detection device 12 (in particular, of the cameras 13 and 14) and, according to some variants, with a unit directly part of the device print 20). Alternatively, the control system 17 is a centralized system external to the detection device 12 and / or to the printing device 20.

According to some non-limiting embodiments, the cameras 13 and 14 are able to identify the edges (4, 5 and 6) and therefore the edges (7 and 8) of article 2. In particular, to identify the edges, use image processing techniques known as "Edge Based Matching". Alternatively or in addition, the edges (7 and 8) can be determined by making the intersection of the edges (4, 5 and 6) and / or using image processing techniques known as "corner detectors".

The image processing techniques known as "Edge Based Matching" are for example described in one of the following documents: Steger, C, Occlusion, clutter, and illumination invariant object recognition. In Kalliany, R., Leberl, F., eds .: International Archives of Photogrammetry, Remote Sensing, and Spatial Information Sciences. Volume XXXIV, part 3A., Graz (2002); Hofhauser, C. Steger, N. Navab, Edge-based Template Matching and Tracking for Perspectively Distorted Planar Objects, Proc. 4th International Symposium on Advances in Visual Computing ISVC '08, 2008; Borgefors, G., 1988. Hierarchical chamfer matching: A parametric edge matching algorithm. IEEE Transactions on Pattern Analysis and Machine Intelligence 10 (6), pp. 849-865; Steger, C., 1998. An unbiased detector of curvilinear structures. IEEE Transactions on Pattern Analysis and Machine Intelligence 20 (2), pp. 113-125; and the patent US7016539B1.

Image processing techniques known as “corner detectors” are for example described in A Combined Corner And Edge Detector, by Chris Harris & Mike Stephens Plessey Research Roke Manor, United Kingdom © The Plessey Company pic. 1988, Proceedings of the 4th Alvey Vision Conference. pp. 147-151 (http://www.bmva.org/bmvc/1988/avc-88-023.pdf).

In some specific and non-limiting cases, cameras are devices that include on-board processing and are known as "smart cameras" (cameras known per se that, in addition to acquiring images, can also perform processing on them to obtain higher information level).

Advantageously but not necessarily, the control system 17 is able to estimate at least the position 21 (and / or 22) on the basis of the image 15 (and / or 16), and is able to translate the predefined pattern 18 to obtain the manipulated pattern 19 depending on position 21 (or 22). In particular, the control system 17 is able to translate the predefined drawing 18 transversely (in particular, perpendicularly; more particularly, in a direction parallel to the X axis) to the direction A of advancement as a function of position 21 (and / or 22 ).

More specifically, the control system 17 is able to estimate at least the position 21 (and / or 22) along the X axis on the basis of image 15 (and / or 16). More precisely, the control system 17 is able to estimate the distance x of position 21 (and / or 22) along the X axis with respect to a reference position 21 '(and / or 22'). For example, this reference position 21 '(and / or 22') is the position of an edge 7 '(and / or 8') of the aforementioned theoretical reference article 2 '. In particular, the control system 17 is adapted to translate the predefined pattern 18 by the distance x.

According to some non-limiting embodiments, the control system 17 is able first to estimate the distance x according to the reference system of the detection device 12 and then to convert the distance x into the reference system of the printing device 20. In alternatively or in addition, the control system 17 is adapted first to estimate the angle θ of inclination according to the reference system of the detection device 12 and then to convert the angle θ of inclination into the reference system of the printing device 20 .

Advantageously but not necessarily, the detection device 12 comprises a sensor 24 which is adapted to detect the presence of the article 2 in (a correct position in) correspondence with the detection station 12. More precisely, sensor 24 which is adapted to detect the presence of article 2 in a correct position in direction A (along axis Y). In particular, in use, when the sensor 24 detects that the article 2 (which moves along the path P in the direction A) reaches the detection station 10, it allows the cameras 13 and 14 to be activated to acquire the images 15 and 16. More specifically, when the sensor 24 detects that the article 2 (which moves along the path P in the direction A) reaches the (correct position in the) detection station 10, the sensor 24 itself emits a signal for activation cameras 13 and 14 (or for the acquisition - by the control system 17) of images 15 and 16.

Advantageously but not necessarily (Figure 4), the detection device 12 also comprises at least one illuminator 25 (preferably several illuminators 25 are provided) oriented towards the determined path P and able to emit illumination towards the article 2 of base. The cameras 13 and 14 and the illuminator 25 are oriented towards the path P determined so that the cameras 13 and 14 do not receive the (directly) reflected illumination from the base article 2 (and / or the conveyor device 9; plus precisely, from the movement plan 23, on which article 2 is laid down). In particular, the illuminator 25 is not oriented perpendicularly to the surface 3 of the basic article 2 arranged at the detection station 10.

Advantageously but not necessarily, the cameras 13 and 14 are oriented towards the path P substantially, perpendicularly to the direction A and, in particular, to the article 2 (and / or to the conveyor device 9; more precisely, to the movement plane 23, on which Article 2 is attached to).

According to some non-limiting forms of implementation (Figure 1), the printing device 20 includes a digital inkjet printer.

Advantageously but not necessarily, the machine 1 is devoid of guides or other elements arranged in correspondence of the path to impose on the article 2 a determined position / orientation (on the movement element).

Advantageously but not necessarily, the movement plane 23 is of a different color from the basic article 2. In this way, the operations of the cameras 13 and 14 and, more precisely, of the control system 17 to identify the edges (4, 5 and 6) of the article 2 and, in particular, the edges (7 and 8) of the Article 2 are facilitated.

According to some non-limiting forms of implementation, the movement plan 23 is dark (black). Typically, article 2 is clear (white-light gray).

In accordance with a second aspect of the present invention (Figure 5), a plant 26 is provided for making a ceramic product 27. In particular, the ceramic product 27 is a slab (more precisely, a tile).

Plant 1 includes machine 1 for decoration; a compacting machine 28 for compacting a powder material CP comprising ceramic powder so as to obtain a layer of compacted powder KP; and a conveyor assembly 29 (in particular, comprising the conveyor device 9), which is adapted to advance (substantially continuously) the powder material CP along a path PP (of which the path P is a section) from a station input 30 to the compacting machine 28 and the compacted powder layer KP (always along the PP path) from the compacting machine 28 to the decoration machine 1 (and to an output station 31). In particular, the compacting machine 28 and the machine 1 are arranged along the path PP between the inlet station 30 and an outlet station 31. More particularly, the machine 1 is arranged downstream of the compacting machine 28.

In particular, the basic article 2 includes (at least) a portion of the compacted powder layer KP.

According to some non-limiting embodiments, the plant 26 comprises at least one cutting unit 32 for transversely cutting the layer of compacted powder KP so as to obtain the basic article 2, which has a portion of the compacted powder layer KP. In particular, the cutting unit 32 is arranged along the path PP (more particularly, downstream of the compacting machine 28 and upstream of the machine 1). Advantageously but not necessarily, the conveyor group 29 is adapted to feed the compacted powder layer KP to the cutting group 32 and to transport the basic article 2 downstream of the cutting group 32 (through the machine 1).

According to some non-limiting embodiments, the plant 26 further comprises a dryer 33 arranged along the path PP downstream of the compacting machine 28 (more precisely, downstream of the cutting unit 32) and upstream of the machine 1 .

According to some non-limiting embodiments, the plant 26 also comprises at least one firing oven 34 for sintering (the layer of compacted powder KP de) the basic article 2 so as to obtain the ceramic product 27. In particular, the cooking oven 34 is arranged along the path P downstream of the machine 1.

According to some forms of implementation not illustrated and not limiting, the plant 26 does not include the compacting machine 28 and the cutting unit 32 but includes a traditional pressing machine (known type) for tiles. Typically, this pressing machine is equipped with an oleodynamic pressing device with a vertical axis adapted to press the ceramic material in powder form so as to directly obtain single slabs (which do not require cuts) of pressed material.

In accordance with a third aspect of the present invention there is provided a method for the surface decoration of a basic article 2 (Figure 1), in particular an article 2 as defined above (in relation to the first aspect of the present invention). Advantageously but not necessarily, the method is implemented by a machine 1 in accordance with the first aspect of the present invention.

The method comprises a first conveying step during which the base article 2 is conveyed along a determined path P, in a direction A of advancement, through a detection station 10 and a printing station 11 arranged downstream of the printing station. detection 10; a detection phase, during which at least one image of the edge 7 and of the edge 8 (more precisely, at least one image 15 of the edge 7 and at least one image 16 of the edge 8) is acquired at the detection station 10 ; and a first processing step, during which a position 21 of the corner 7 and a position 22 of the edge 8 are detected (estimated) as a function of the acquired image (more precisely, of the images 15 and 16, respectively), and the position (in particular, the orientation) of the basic article 2 with respect to the direction A of advancement is estimated as a function of positions 21 and 22.

According to some non-limiting forms of implementation, during the first processing phase, the edges (4, 5 and 6) (and therefore the edges 7 and 8 of article 2) are identified. In particular, image processing techniques known as “Edge Based Matching” are used to identify edges. Alternatively or in addition, the edges (7 and 8) are determined by making the intersection of the edges (4, 5 and 6) and / or using image processing techniques known as "corner detectors".

In some specific and non-limiting cases, cameras are devices that include on-board processing and are known as "smart cameras".

The method also comprises a second processing step, during which a predefined drawing 18 is moved (in particular, rotated) as a function of (what is detected during the detection step and) what is obtained during the first processing step so to obtain a manipulated design 19 (coordinated with the orientation / estimated position of article 2); and a printing phase, during which the manipulated design 19 is applied to the surface 3 of the basic article 2. Advantageously but not necessarily, a matrix camera 13 acquires the image 15 and a matrix camera 14 acquires the image 16.

In particular (Figure 1), the position 21 of the corner 7 and the position 22 of the corner 8 are estimated on the basis of images 15 and 16.

According to some non-limiting embodiments, during the first processing phase, an angle θ of inclination of the basic article 2 (more precisely, of the edge 6) with respect to the direction A of advancement is estimated, in particular as a function of the position 21 and position 22. More specifically, the inclination angle θ is estimated with respect to a theoretical reference article 2 '(arranged and oriented as hypothetically correct along the path P - in particular, with its longitudinal extension parallel to the direction A). More precisely, article 2 'has edges 4' and 6 'substantially parallel to direction A (and edge 5' substantially perpendicular to direction A).

In particular, during the second processing phase, the predefined design 18 is rotated according to the inclination (orientation) estimated to obtain the manipulated design 19.

According to some non-limiting embodiments, the inclination (the orientation or, more precisely, the inclination angle θ) is estimated by interpolating the positions 21 and 22 and (knowing the shape of the article 2) by determining the angle between the interpolating curve (straight line) and direction A). In addition or alternatively, the inclination (the orientation or, more precisely, the inclination angle θ) is estimated (knowing the shape of the article 2) on the basis of the differences between the X and Y coordinates of the positions 21 and 22.

In some specific and non-limiting cases, during the second processing phase, the default design 18 is rotated by the angle θ of inclination.

In particular, the control system 17 is adapted to determine the X and Y coordinates on the basis of what is detected by the cameras 13 and 14. More particularly, the X and Y coordinates are determined in a reference system of the cameras 13 and 14. Even more particularly, this reference system is a pixel reference system (as a unit of measurement).

According to some non-limiting embodiments, during the first processing phase the (coordinates of) positions 21 and 22, acquired in the reference system of the cameras 13 and 14 (in pixels), are converted into positions according to a reference system used for the printing phase (in millimeters).

Typically, this conversion is carried out by means of a function, in particular matrix (more particularly, with coefficients determined during a calibration phase - described in more detail below - and knowing the thickness of the article 2).

According to some non-limiting embodiments, during the first processing phase, at least position 21 (and / or position 22) is estimated in a transverse direction, in particular orthogonal to the direction A of advancement. According to some non-limiting forms of implementation, during the second processing phase, the default design 18 is translated (moved) according to position 21 (and / or position 22).

In particular, during the second processing phase, the predefined drawing 18 is translated transversely (in particular, perpendicularly; more particularly, in a direction parallel to the X axis) to the direction A of advancement as a function of position 21 (and / or the position 22).

More specifically, during the first processing phase, at least position 21 (and / or position 22) along the X axis on the basis of image 15 (or 16). More precisely, during the first processing phase, the x distance of position 21 (and / or position 22) along the X axis with respect to a reference position 21 '(and / or 22') is estimated. For example, this reference position 21 '(and / or 22') is the position of an edge 7 '(and / or 8') of the aforementioned theoretical reference article 2 '. In particular, during the second processing step, the predefined drawing 18 is translated by the distance x.

According to some non-limiting embodiments, during the first processing phase, first the distance x according to the reference system of the cameras 13 and 14 (in pixels) is estimated and then the distance x is converted into the reference system used during the printing phase (in mm). Alternatively or in addition, the angle θ of inclination according to the reference system of the cameras is first estimated and then converted into the system used during the printing phase.

Typically, this conversion is carried out by means of a function, in particular matrix (more particularly, with coefficients determined during a calibration phase and knowing the thickness of the article 2).

Advantageously but not necessarily, during the conveying phase, the basic article 2 is conveyed with a substantially continuous motion (not step by step).

Advantageously but not necessarily, the detection phase, the first and second processing phases are carried out in less than 10 seconds, in particular, in less than 6 seconds (more precisely, from 1 to 10 seconds; even more precisely, from 3 to 6 seconds). Considering that the distance between the detection station 10 and the printing station 11 is typically about 1 meter and that the article 2 is conveyed along the path P at a speed of about 10-20 meters per minute, in this way, it is possible to apply the manipulated drawing 19 on the article 2 without stopping the article 2 itself.

Preferably but not necessarily, the aforementioned control system 17 is capable of carrying out its activities (first and second processing stages) within the times indicated above. In this context, advantageously, the control system 17 comprises a suitable graphics card.

According to some non-limiting embodiments, the method comprises a first calibration step, which precedes the detection step and during which at least one reference drawing 35 is printed (by the printing device 20) on a surface of a control substrate at the printing station 11 (in particular, by means of printing device 20) so as to obtain a printed substrate 36. In particular, while the reference drawing 35 is printed, the control substrate is advanced along the path P (through the printing station 11) and maintained in a predetermined position and orientation by guide elements (e.g. a stop - not shown).

Advantageously but not necessarily, the control substrate has larger (preferably larger) dimensions (width and length) than the basic article 2.

Furthermore, during the first calibration phase, the cameras 13 and 14 detect the reference drawing 35 present on the printed substrate 36; a correspondence function (in particular, matrix) is created between a reference system used while the reference drawing is printed (by the printing device 20) and a reference system used while the reference drawing 35 is detected (by the cameras 13 and 14) on the basis of what is detected by the cameras 13 and 14 during the calibration phase and of the data relating to the reference drawing 35 (more precisely, the data used during the printing of the reference drawing 35). In particular, the correspondence function between the two aforementioned reference systems is obtained using known calibration algorithms (for example described in Tsai R Y．A versatile camera calibration technique for high-accuracy 3D machine vision metrology using off-the- shelf TV cameras and lenses. IEEE Journal of Robotics and Automation ， 1987 ， 3 (4) ： 323—344; Zhang Zhengyou; Flexible camera calibration by viewing a plane from unknown orientations ∥International Conference on Computer Visbn (1CCV). Proceedings Seventh International Conference on Computer Vision ．Liege ， Belgium ： Elsevier Science Publishers ， 1999 ： 666-674; Chen Shengyong, Liu Sheng. Implementation of Computer Vision Technology Based on OpenCV. Beijing: Science Press, May, 2008); Jean-Yves Bouguet. Camera calibration toolbox for Matlab [OBIOL]. 2012. http://www.vision.caltech.edu/Bouguetj/calib_doc; David A. Forsyth, Jean Ponce. Computer Vision: A Modern Approach. Person Education, Inc. 2004).

According to some non-limiting embodiments, during the first calibration phase, the printed substrate 36 is conveyed (by a conveyor device 9) along the path P determined in the direction A of advancement through the detection station 10 (at which the cameras 13 and 14 are arranged and the reference drawing 35 is detected). Advantageously but not necessarily, at least one guide 37 (e.g. a stop) keeps the substrate 36 in a predetermined position and orientation as it passes through the detection station 12 (and the cameras 13 and 14 detect the reference pattern 35 present on the substrate printed 36).

According to some embodiments not illustrated, at least one guide (or a stop) allows the control substrate to be kept in a predetermined position and orientation as it passes through (is arranged at the) printing station 20 (and the drawing of reference 35 is printed, in particular by the printing device 20).

Advantageously but not necessarily, during the first calibration phase, the following are detected: the position of at least one point 38 in correspondence with a first area of the reference drawing 35 (in particular, near the edge 7), the position of at least one point 39 of the reference drawing in correspondence with a second zone (in particular, near the corner 8). In other words, the point 38 which is approximately in the position in which the edge 7 should be found during the detection phase and the point 39 which is approximately in the position in which the edge 8 should be found during the detection phase are detected. detection.

In particular, in these cases, the positions (the coordinates) of the points 38 and 39 are used to relate (as explained above) the reference system used while the reference drawing is printed (from the printing device 20) and the reference system used while the reference drawing is detected (from cameras 13 and 14).

According to specific non-limiting forms of implementation, the reference drawing 35 includes at least one chessboard (more precisely, two chessboards). The chessboard (which is printed by the printing device 20) allows the cameras to be calibrated with the known methods. Furthermore, points 38 and 39 allow to establish a correspondence between the reference systems of cameras 13 and 14 (for example as described in Zhang Ling, Yin Muyi, Li Wei1, Liu Hailin, 2014; Applied Mechanics and Materials Implementation of Camera Calibration Method Based on OpenCV; Applied Mechanics and Materials; ISSN: 1662-7482, Vols. 602-605, pp 3796-3799; doi: 10.4028 / www.scientific.net / AMM.602-605.3796).

Advantageously but not necessarily, the method comprises a second calibration step, which in turn comprises a conveying sub-step, during which a control substrate 40 (different or the same as the one previously mentioned) is conveyed along the determined path P, in the feed direction A, with its own leading edge 41 arranged at least partially anteriorly in the feed direction A with respect to the other edges of the control substrate 40, and through the printing station 11, in correspondence with which a printing device 20 is arranged .

The second calibration step also comprises an actuation step, during which, while the control substrate 40 passes through the printing station 11, the printing device 20 is operated so as to apply at least one reference mark 42 on the control substrate 40 as a function of an indication of the position of control substrate 40 along path P so as to obtain a marked substrate 43.

For example, the printing device 11 is operated according to the presumed position of the control substrate 40 given by the advancement of the conveyor device 9. Alternatively or in addition, a sensor (for example a photocell) is provided at the entrance to the station printing 11 to detect the passage of objects (more precisely, of the control substrate 40); the printing device 11 is operated on the basis of what is detected by this sensor (in other words, what is detected by the sensor acts as an indication of the position of the control substrate 40 along the path P).

The second calibration step also includes a measurement sub-step, during which the distance between the mark 42 and the leading edge 41 is measured and a comparison is made with a reference distance (at which the mark 42 should have been printed with respect to the front edge 41); and an adjustment sub-phase, during which the function that links the operation of the printing device 20 to the indication of the position of the control substrate 40 along the path P is modified on the basis of the aforementioned comparison.

In particular, if the sign 42 is too far from the front edge 41, the actuation of the printing device 20 is anticipated; on the contrary, if the sign 42 is too close to the front edge 41, the actuation of the printing device 20 is postponed.

According to some non-limiting forms of implementation, the method also includes a pre-calibration phase, which is, in particular, prior to the calibration phase. During the pre-calibration phase, the intrinsic parameters for each camera 13 and 14 are determined (separately) with known procedures. More precisely, each camera 13 and 14 is made to acquire an image of known size.

Basically, the pre-calibration phase allows me to individually calibrate each camera 13 and 14; the first calibration phase allows you to cumulatively calibrate the detection device 12 (cameras 13 and 14) together with the printing device 20 in particular as regards the position along the X axis and the angle θ of inclination; and the second calibration phase allows you to calibrate the operation of the printing device 20 and therefore the printing of the manipulated design along the Y axis.

In accordance with a further aspect of the present invention, a method for manufacturing a ceramic product 27 is provided. This method comprises a method for surface decoration according to the third aspect of the present invention and comprises a firing step, which is subsequent to the printing phase and during which the basic article 2 is sintered (the compacted powder layer KP de) so as to obtain the ceramic product 27.

According to some non-limiting embodiments, the method also comprises a compacting step, which precedes the printing step and during which a powder material CP comprising ceramic powder is compacted so as to obtain a layer of compacted powder KP .

Advantageously but not necessarily, the method for making the ceramic product 27 is implemented by the plant 26 described above (in accordance with the second aspect of the present invention).

Unless the contrary is explicitly indicated, the content of the references (articles, books, patent applications, etc.) cited in this text is referred to here in its entirety. In particular, the aforementioned references are incorporated herein by reference.

Claims (1)

1.- Machine for the surface decoration of a basic article (2) of the ceramic processing industry having at least one surface (3), a first, a second and at least a third edge (4, 5, 6), which they are joined together so as to define a first and at least a second edge (7, 8) (corner); in particular, the basic article (2) includes ceramic material; in particular, the first and second edges (4, 5) join in order to define the first edge (7), the second and third edges (5, 6) join in order to define the second edge (8) ; the machine (1) comprises a conveyor device (9) for conveying the basic article (2) along a determined path (P), in a direction (A) of travel, through a detection station (10) and a station printing station (11) arranged downstream of the detection station (10); the machine (1) being characterized by the fact that it comprises: a detection device (12), which is arranged in correspondence with the detection station (10) and comprises a first and a second matrix camera (13, 14), which are adapted to acquire a first image (15) of the first edge (7) and a second image (16) of the second edge (8), respectively; a control system (17), which is able to move a predefined design (18) on the basis of the first image (15) and the second image (16) acquired by the first and second matrix cameras (13, 14) in so as to obtain a manipulated drawing (19); a printing device (20), which is able to apply (apply) the manipulated design (19) on the surface (3) of the base article (2). 2.- Machine according to Claim 1, in which the control system (17) is able to estimate a first position (21) of the first edge (7) and a second position (22) of the second edge (8) on the basis of the first and of the second image (15, 16), and is adapted to estimate the orientation of the basic article (2) with respect to the direction (A) of advancement as a function of the first and second position (21, 22) so as to obtaining an estimated orientation, and is adapted to rotate the predefined design (18) to be brought onto said surface (3) as a function of the estimated orientation to obtain the manipulated design (19). 3.- Machine according to Claim 2, in which the control system (17) is able to estimate an angle (θ) of inclination of the basic article (2) with respect to the direction (A) of advancement, in particular as a function of the first and second position (21, 22). 4.- Machine according to any one of the preceding claims, in which the control system (17) is able to estimate a first position (21) of at least the first edge (7) on the basis of the first image (15), and is adapted to translating the predefined design (18) transversely (in particular perpendicularly) to the direction (A) of advancement as a function of the first position (21) to obtain the manipulated design (19). 5.- Machine according to any one of the preceding claims, in which the detection device (12) comprises an illuminator (25) oriented towards the determined path (P) and able to emit an illumination towards the base article (2) ; the first and second cameras (13, 14) being oriented towards the path (P) determined so as not to receive the reflected lighting from the basic article (2); in particular, the illuminator (25) not being oriented perpendicularly to said surface (3) of the base article (2) arranged at the detection station (11). 6.- Method for the surface decoration of a basic article (2) of the ceramic processing industry with at least one surface (3), a first, a second and at least a third edge (4, 5, 6), which they are joined together so as to define a first and at least a second edge (7, 8) (corner); in particular, the basic article (2) includes ceramic material; in particular, the first and second edges (4, 5) join in order to define the first edge (7), and the second and third edges (5, 6) join in order to define the second edge (8 ); the method comprises a first conveying step during which the base article (2) is conveyed along a determined path (P), in a direction (A) of advancement, through a detection station (10) and a print (11) arranged downstream of the detection station (10); the method being characterized by the fact that it includes: a detection step, during which at least a first image (15) of the first edge (7) and at least a second image (16) of the second edge (8) are acquired at the detection station (10); a first processing step, during which a first position (21) of the first edge (7) and a second position (22) of the second edge (8) are estimated as a function of the first and second image (15, 16), respectively; a second processing phase, during which a predefined drawing (18) to be reproduced on said surface (3) of the basic article (2) is moved according to what is obtained during the first processing phase in order to obtain a drawing manipulated (19); and a printing phase, during which the manipulated design (19) is affixed (applied) to the surface (3) of the basic article (2). 7.- Method according to Claim 6, wherein, during the detection step, a first matrix camera (13) acquires the first image (15) of the first edge (7) and a second matrix camera (14) acquires the second image (16) of the second edge (7). 8.- Method according to Claim 6 or 7, wherein, during the first processing step, the orientation of the base article (2) with respect to the feed direction (A) is estimated as a function of the first position (21) and of the second position (22); during the second processing phase, the default design is rotated according to the estimated orientation. 9.- Method any one of claims 6 to 8, in which, during the first processing step, at least the first position (21) of the first edge (7) is estimated at least in a transverse direction, in particular orthogonal, to the direction ( A) advancement; during the second processing step the predefined drawing (18) is moved, in particular translated, according to the first position (21). 10.- Method according to any one of claims 6 to 9, in which, during the first processing step, an angle (θ) of inclination of the basic article (2) with respect to the direction (A) of advancement is estimated (in particular, according to the first and second position); in particular, the angle (θ) of inclination with respect to an orientation of a reference article (2) is estimated, in particular oriented in the direction (A) of advancement; during the second processing phase, the default design (18) is rotated by the estimated inclination angle (θ). 11. A method according to any one of claims 6 to 10, and comprising a first calibration step, which precedes the detection step and during which at least one reference design (35) is printed on a surface of a substrate control at the printing station (11); said first matrix camera (13) and second matrix camera (14) detect the reference pattern (35) present on the printed substrate (36); a function of correspondence is created between a reference system used while the reference drawing is printed and a reference system used while the reference drawing is detected on the basis of what is detected by the first matrix camera (13) and by the second camera ( 14) matrix and the data relating to the reference drawing (35). 12.- Method according to Claim 11, in which, during the first calibration phase, the following are detected: the position of at least a first point (38) in correspondence with a first area of the reference drawing (35) in proximity to the first edge (7), the position of at least a second point (39) of the reference drawing (35) in correspondence with a second area of the reference drawing (35) in proximity to the second edge (8). 13. A method according to Claim 12, wherein a first matrix camera (13) detects the position of the first point (38) and a second matrix camera (14) detects the second point (39). 14. A method according to any one of claims 6 to 13, and comprising a second calibration step, which in turn comprises a conveying sub-step, during which a control substrate (40) is conveyed along the path (P ) determined, in the feed direction (A), with its own leading edge (41) arranged at least partially anteriorly in the feed direction (A) with respect to the other edges of the control substrate (40), and through the printing station (11 ), in correspondence with which a printing device (20) is arranged; an actuation sub-phase, during which, while the control substrate (40) passes through the printing station (11), the printing device (20) is operated so as to apply at least one reference mark (42) on the control substrate as a function of an indication of the position of the control substrate (40) along the path (P) and so as to obtain a marked substrate (43); a measurement sub-step, during which the distance between the mark (42) and the leading edge (41) is measured and a comparison is made with a reference distance; an adjustment sub-phase, during which the function that links the operation of the printing device (20) to the indication of the position of the control substrate (40) along the path (P) determined is modified on the basis of said comparison. 15.- Method according to any one of claims 6 to 14, and implemented by a machine (1) for the surface decoration of a basic article (2) according to one of claims 1 to 5.